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MicroSD interface filter fits mobile, computing devices

Posted: 09 Jul 2009 ?? ?Print Version ?Bookmark and Share

Keywords:interface? filter protection? microSD?

California Micro Devices Corp. has announced the CM1624, an application specific microSD interface protection filter for mobile and computing devices. The CM1624 protects the microSD memory card user interface against ESD damage to the card or to the hardware, and suppresses EMI while providing digital signal integrity.

The new microSD interface protection filter is a member of the Praetorian III product line and combines filter performance with minimal line capacitance. The CM1624 also features integrated pull-up resistors, eliminating the need for additional circuitry on the handset PCB and saving BOM cost.

Inductor-based filter solutions offer the highest level of digital signal integrity available. The CM1624 can support clock frequencies up to 96MHz, rise/fall times at 5ns and high levels of attenuation from 700MHz to 3GHz. The CM1624 pinout is optimized for the microSD interface standard and features 6 lines of EMI suppression with IEC 61000-4-2 +/-15kV (contact) integrated ESD protection, one line of through package ESD protection for the Vcc line, and two additional discrete ESD diodes for related functions such as Card Detect. Additionally, CMD has integrated 25k pull-up resistors to help detect the presence of the memory card.

As process geometries used in manufacturing baseband and applications processors migrate to increasingly smaller feature sizes, system operating voltages are also becoming lower so that the amount of capacitive loading on the data lines has become a major concern for handset designers. The microSD interface specification allows for a total capacitive loading budget of 40pF, and traditional filter architectures consume too much of this tight design parameter. The CM1624 features a specification 0V DC capacitance of 20pF, and less than 12pF at operating voltage.

The CM1624-08DE is available in an industry standard, compact, RoHS-compliant microDFN16 package. Samples are available now and are priced at $0.16 each in 3,000 units. The CM1624 is qualified for mass production now.

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